1. Field of the Invention
The present invention relates to data storage devices such as disk drives. The invention particularly relates to a load beam that allows gimbaling along pitch and roll axes, and that utilizes an inexpensive spherical gimbal ball pressed into an etched hole in the load beam to provide a highly accurate and measurable pivot location of a slider.
2. Description of Related Art
In a conventional disk drive, a read/write head is secured to a rotary actuator magnet and a voice coil assembly by means of a suspension and an actuator arm, and is positioned over a surface of a data storage disk. In operation, a lift force is generated by the aerodynamic interaction between the head and the disk. The lift force is opposed by a counteracting spring force applied by the suspension, such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the disk.
The suspension includes a load beam and a flexure secured to a cantilevered end of the load beam. A slider is mounted to the flexure. The flexure provides a proper pivotal connection for the slider so that during operation, the slider can compensate for irregularities in the disk drive manufacture and operation, by pitching and/or rolling slightly in order to maintain the air bearing, while maintaining appropriate stiffness against yaw movement. Roll is defined as the rotation about an axis extending directly out from the actuator arm through the pivot contact point and parallel to the X-Y plane of the disk. Pitch is defined as rotation about an axis perpendicular to the roll axis through the pivot contact point and parallel to the X-Y plane of the disk. Yaw is gyration around an axis perpendicular to the air-bearing surface. The flexure has to achieve low enough pitch and roll stiffness for the air bearing flying height tolerances while at the same time achieving high enough yaw stiffness for track seeking.
Exemplary suspension designs are illustrated by the following references:
U.S. Pat. No. 5,786,961 to Goss; PA1 U.S. Pat. No. 5,675,454 to Hatanai et al.; PA1 U.S. Pat. No. 5,572,385 to Kuwamoto; PA1 U.S. Pat. No. 5,504,640 to Hagen; PA1 U.S. Pat. No. 5,381,288 to Karam, II; PA1 U.S. Pat. No. 4,811,143 to Ohashi et al.; PA1 U.S. Pat. No. 4,017,898 to Toombs et al.; PA1 U.S. Pat. No. 3,422,412 to Linsley; PA1 U.S. Pat. No. 3,403,388 to Linsley; PA1 U.S. Pat. No. 3,202,772 to Thomas, Jr.; PA1 U.S. Pat. No. 3,183,810 to Sampson; and PA1 U.S. Pat. No. 3,158,847 to Pulkrabek.
In some conventional suspensions, the flexure includes a dimple that abuts against the load beam. In other suspensions, the dimple is formed in the load beam and pushes against the flexure. In these conventional suspensions, the dimple can be formed by stamping either the flexure or the load beam.
A stamped dimple presents several shortcomings, a few of which are mentioned herein. The dimple stamping process is necessarily separate from the process of etching the reference datum holes in the load beam or flexure. Stamping tooling accuracy causes variation between the datum holes and the stamped dimple. Additional variation is added in the case of flexures with stamped dimples when aligning/welding the flexure to the load beam. Further variance occurs when locating/aligning the mount plate to the load beam. Print tolerance shows a boss outer diameter to the load beam hole to be approximately in the range of .+-.0.0015 inch. Yet more variations exist between the concave side of the dimple that can be seen after assembly, and the actual contact point on the convex side that cannot be seen or measured after assembly. This latter variation can be approximately 0.0005 inch. In addition, measurement repeatability of stamped dimples is poor.
Another method of forming the dimple is to etch the load beam. While the dimple location is accurate relative to the datum holes in the load beam, the etched dimple approach presents several drawbacks, some of which are listed herein. The dimple formed by partially etching the load beam does not form a dome. Rather, its top surface is generally flat and circular. The contact point of the dimple and the flexure cannot be very accurately located, as it can be positioned along the circular top portion of the dimple. Once the suspension is assembled, the dimple location will no longer be measurable since the gimbal will no longer be visible for inspection. Forming of a partial etch area is still required to get the dimple to protrude forward in order to get the separation between the flexure/slider and the load beam, in order to achieve gimbaling.
In another design proposed in U.S. Pat. No. 5,786,961, supra, the suspension includes a load beam having proximal and distal ends and a bearing cover portion. A gimbal on the distal end of the load beam has a flexure pad with a slider-engaging first surface and a second surface opposite the first surface. A ball-receiving hole extends through the flexure pad, and a ball is mounted in the ball-receiving hole. The ball has a load point portion that extends from the second surface of the flexure pad and that engages the bearing cover portion of the load beam. The ball is obscured at assembly, which prevents direct location measurement after assembly, and also prevents viewing from the backside to aid in the assembly.
In yet another design proposed in U.S. Pat. No. 5,381,288, supra, the suspension includes a load beam and a spring assembly that are integrally formed. The spring assembly has a bonding tab suspended within the plane of the load beam by two flexible longitudinal arms connected to two flexible transverse arms. The flexible arms permit the bonding tab to roll about the longitudinal axis and pitch about the transverse axis, while preventing the bonding tab from sticking in an off-axis position. The bonding tab defines an aperture that receives a protuberance of the magnetic head to precisely index the magnetic head with the bonding tab, and thus center the magnetic head about a load support point. This design requires a V-shaped cross-slot to be machined in the slider into which the ball nests for registration.
The foregoing two proposed designs add cost, complexity to the design and assembly of the suspension, and lack optical measurement accessibility after assembly. Therefore, these designs do not appear to be suitable for next generation disk drives where simplicity and low cost will likely become primary considerations for successful head designs.